<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        h1 {
            font-weight: 300;
            font-size: 1.8em;
            margin-top: 0;
        }
        a {
            color: #fff;
        }
        .draggable-header-view {
            background-color: #fff;
            box-shadow: 0 4px 16px rgba(0,0,0,.15);
            width: 320px;
            height: 560px;
            overflow: hidden;
            margin: 30px auto;
            position: relative;
            font-family: 'Roboto', Helvetica, Arial, sans-serif;
            color: #fff;
            font-size: 14px;
            font-weight: 300;
            -webkit-user-select: none;
            -moz-user-select: none;
            -ms-user-select: none;
            user-select: none;
        }
        .draggable-header-view .bg {
            position: absolute;
            top: 0;
            left: 0;
            z-index: 0;
        }
        .draggable-header-view .header, .draggable-header-view .content {
            position: relative;
            z-index: 1;
            padding: 30px;
            box-sizing: border-box;
        }
        .draggable-header-view .header {
            height: 160px;
        }
        .draggable-header-view .content {
            color: #333;
            line-height: 1.5em;
        }
    </style>
</head>
<body>
<script src="https://cdn.bootcss.com/vue/2.2.2/vue.min.js"></script>

<script type="text/x-template" id="header-view-template">
    <div class="draggable-header-view"
         @mousedown="startDrag" @touchstart="startDrag"
         @mousemove="onDrag" @touchmove="onDrag"
         @mouseup="stopDrag" @touchend="stopDrag" @mouseleave="stopDrag">
        <svg class="bg" width="320" height="560">
            <path :d="headerPath" fill="#3F51B5"></path>
        </svg>
        <div class="header">
            <slot name="header"></slot>
        </div>
        <div class="content" :style="contentPosition">
            <slot name="content"></slot>
        </div>
    </div>
</script>

<div id="app" @touchmove.prevent>
    <draggable-header-view>
        <template slot="header">
            <h1>Elastic Draggable SVG Header</h1>
            <p>with <a href="http://vuejs.org">Vue.js</a> + <a href="http://dynamicsjs.com">dynamics.js</a></p>
        </template>
        <template slot="content">
            <p>Note this is just an effect demo - there are of course many additional details if you want to use this in production, e.g.
                handling responsive sizes, reload threshold and content scrolling. Those are out of scope for this quick little hack. However,
                the idea is that you can hide them as internal details of a Vue.js component and expose a simple Web-Component-like interface.
            </p>
        </template>
    </draggable-header-view>
</div>

<script>
    Vue.component('draggable-header-view', {
        template: '#header-view-template',
        data: function () {
            return {
                dragging: false,
                // quadratic bezier control point
                c: { x: 160, y: 160 },
                // record drag start point
                start: { x: 0, y: 0 }
            }
        },
        computed: {
            headerPath: function () {
                return 'M0,0 L320,0 320,160' +
                    'Q' + this.c.x + ',' + this.c.y +
                    ' 0,160'
            },
            contentPosition: function () {
                var dy = this.c.y - 160
                var dampen = dy > 0 ? 2 : 4
                return {
                    transform: 'translate3d(0,' + dy / dampen + 'px,0)'
                }
            }
        },
        methods: {
            startDrag: function (e) {
                e = e.changedTouches ? e.changedTouches[0] : e
                this.dragging = true
                this.start.x = e.pageX
                this.start.y = e.pageY
            },
            onDrag: function (e) {
                e = e.changedTouches ? e.changedTouches[0] : e
                if (this.dragging) {
                    this.c.x = 160 + (e.pageX - this.start.x)
                    // dampen vertical drag by a factor
                    var dy = e.pageY - this.start.y
                    var dampen = dy > 0 ? 1.5 : 4
                    this.c.y = 160 + dy / dampen
                }
            },
            stopDrag: function () {
                if (this.dragging) {
                    this.dragging = false
                    dynamics.animate(this.c, {
                        x: 160,
                        y: 160
                    }, {
                        type: dynamics.spring,
                        duration: 700,
                        friction: 280
                    })
                }
            }
        }
    })

    new Vue({ el: '#app' })
</script>
</body>
</html>